You can have
drop down folders in the bookmark toolbar.
Here's how to get them.
Find a website you want to bookmark (ex. Msg Plus! Forums)
Go to Bookmarks > Bookmark this page
You should have something like this.
Make sure you click on the arrow to view the folders.
Click on
New Folder
Name the folder what ever you would like. This is the folder that will be on the toolbar.
Add some links to the folder (in Manage Bookmarks) and you should be fine.
Hope that helps!